1. Field of the Invention
The present invention relates to the device structure of a magnetic sensor and a method for manufacturing the same, both of which are conducive to miniaturization of the magnetic sensor.
2. Description of the Related Art
There is proposed the device structure of a magnetic sensor which is configured by forming a magnetic sensor portion having a magnetoresistance effect and a signal processing circuit portion which reads out the signal of the magnetic sensor portion on the same substrate; and in recent years, in the stream where miniaturization and an increase in performance of such a magnetic sensor device are advanced, the development of a magnetic sensor having a monolithic structure as disclosed in, for example, Japanese Unexamined Patent Publication No. 2004-264205 (Patent Document 1) or Japanese Unexamined Patent Publication No. 2009-076888 (Patent Document 2) is actively performed.
On the other hand, in the magnetic sensor device having this monolithic structure, the electrical signal from the magnetic sensor portion is read out by the signal processing circuit; and thus, for example, an electrical coupling portion which uses a metal wiring made of, for example, aluminum or the like is needed. The aforementioned Patent Document 1 discloses the device structure of the magnetic sensor which uses aluminum as the metal wiring layer and forms magnetic material directly on the metal wiring layer.
In the device structure of this magnetic sensor, miniaturization of a contact portion to be electrically coupled to the signal processing circuit portion is difficult in the advancement of miniaturization of the magnetic sensor device. More specifically, in order to secure a contact resistance value nearly equal to a conventional type, a contact area equal to a conventional one is needed. Thus, the area percentage of a contact region occupied in the whole magnetic sensor portion increases as the miniaturization of the magnetic sensor device is advanced. Accordingly, the device structures disclosed in Patent Document 1 and Patent Document 2 can be said to be a structure which is inept in the miniaturization of the magnetic sensor.
[Patent Document 1] Japanese Unexamined Patent Publication No. 2004-264205 (see FIG. 4 of Patent Document 1)
[Patent Document 2] Japanese Unexamined Patent Publication No. 2009-076888
As described above, in the device structure of the conventional magnetic sensor disclosed in Patent Document 1, when the contact portion having electrical coupling with the magnetic material is miniaturized, an increase in contact resistance is caused and accordingly the advancement of the miniaturization of the magnetic sensor device is difficult. More specifically, the increase in contact resistance due to a reduction in contact area leads to that parasitic resistance of the contact portion cancels a resistance changing rate of the magnetic sensor in appearance, and sensitivity of the magnetic sensor deteriorates.